1. Field of the Invention
The present invention relates to the design and generation of multimeric cytokines that retain in vitro activity and show enhanced in vivo efficacy. In preferred embodiments, the dock-and-lock (DNL) method is used to produce tetrameric cytokines that are anchored on a humanized monoclonal antibody or fragment thereof (MAb) by site-specific conjugation of a cytokine-based DDD moiety with a recombinant IgG, in which each of the two antibody heavy chains is fused to an AD moiety and dimers of the DDD moiety bind to each AD moiety. In a more preferred embodiment, the cytokine is erythropoietin, granulocyte colony-stimulating factor (G-CSF) or interferon-α2b (IFNα2b), although the disclosed methods may be used to produce DNL constructs comprising any tetrameric cytokine and antibody or fragment. In a most preferred embodiment, a humanized anti-CD20 MAb (hA20) is conjugated to IFNα2b to form a 20-2b DNL construct that comprises four copies of IFNα2b. The cytokine-MAb constructs are of use to treat a variety of disease states and show greater potency against target cells, such as tumors, than the parent MAb alone, the cytokine alone, a non-conjugated combination of MAb and cytokine or cytokine conjugated to a control MAb.
2. Related Art
IFNα2b
Interferon-α (IFNα) has been reported to have anti-tumor activity in both animal models of cancer (Ferrantini et al., 1994, J Immunol 153:4604-15) and human cancer patients (Gutterman et al., 1980, Ann Intern Med 93:399-406). IFNα can exert a variety of direct anti-tumor effects, including down-regulation of oncogenes, up-regulation of tumor suppressors, enhancement of immune recognition via increased expression of tumor surface MHC class I proteins, potentiation of apoptosis, and sensitization to chemotherapeutic agents (Gutterman et al., 1994, PNAS USA 91:1198-205; Matarrese et al., 2002, Am J Pathol 160:1507-20; Mecchia et al., 2000, Gene Ther 7:167-79; Sabaawy et al., 1999, Int J Oncol 14:1143-51; Takaoka et al, 2003, Nature 424:516-23). For some tumors, IFNα can have a direct and potent anti-proliferative effect through activation of STAT1 (Grimley et al., 1998 Blood 91:3017-27). Indirectly, IFNα can inhibit angiogenesis (Sidky and Borden, 1987, Cancer Res 47:5155-61) and stimulate host immune cells, which may be vital to the overall antitumor response but has been largely under-appreciated (Belardelli et al., 1996, Immunol Today 17:369-72). IFNα has a pleiotropic influence on immune responses through effects on myeloid cells (Raefsky et al, 1985, J Immunol 135:2507-12; Luft et al, 1998, J Immunol 161:1947-53), T-cells (Carrero et al, 2006, J Exp Med 203:933-40; Piling et al., 1999, Eur J Immuol 29:1041-50), and B-cells (Le et al, 2001, Immunity 14:461-70). As an important modulator of the innate immune system, IFNα induces the rapid differentiation and activation of dendritic cells (Belardelli et al, 2004, Cancer Res 64:6827-30; Paquette et al., 1998, J Leukoc biol 64:358-67; Santini et al., 2000, J Exp med 191:1777-88) and enhances the cytotoxicity, migration, cytokine production and antibody-dependent cellular cytotoxicity (ADCC) of NK cells (Biron et al., 1999, Annu Rev Immunol 17:189-220; Brunda et al. 1984, Cancer Res 44:597-601).
The promise of IFNα as a cancer therapeutic has been hindered primarily due to its short circulating half-life and systemic toxicity. PEGylated forms of IFNα2 display increased circulation time, which augments their biological efficacy (Harris and Chess, 2003, Nat Rev Drug Discov 2:214-21; Osborn et al., 2002, J Pharmacol Exp Ther 303:540-8). Fusion of IFNα to a monoclonal antibody (MAb) can provide similar benefits as PEGylation, including reduced renal clearance, improved solubility and stability, and markedly increased circulating half-life. The immediate clinical benefit of this is the requirement for less frequent and lower doses, allowing prolonged therapeutic concentrations. Targeting of IFNα to tumors using MAbs to a tumor-associated antigen (TAA) can significantly increase its tumor accretion and retention while limiting its systemic concentration, thereby increasing the therapeutic index. Increased tumor concentrations of IFNα can augment its direct antiproliferative, apoptotic and anti-angiogenic activity, as well as prime and focus an antitumor immune response. Studies in mice using syngeneic murine IFNα-secreting transgenic tumors demonstrated an enhanced immune response elicited by a localized concentration of IFNα (Ferrantini et al., 2007, Biochimie 89:884-93).
G-CSF
Granulocyte colony-stimulating factor (G-CSF) stimulates the production of neutrophils and regulates the survival, proliferation, and differentiation of hematopoietic progenitors. In the U.S., a recombinant methionyl human G-CSF and its longer-acting PEGylated form are used primarily for treating chemotherapy-induced neutropenia to directly increase neutrophil counts and for mobilizing transplantable stem cells from bone marrow to the blood for easier collection and processing.
Erythropoietin
Erythropoietin (Epo) is a hematopoietic growth factor that stimulates the proliferation and differentiation of erythrocytes into mature red blood cells. Several recombinant human Epo are currently used for the treatment of anemia, predominantly associated with chronic renal failure and post cancer chemotherapy. However, the short half-life (4-13 hours) of rhEpo necessitates frequent dosing and, therefore, increasing the serum half-life of Epo to allow less frequent dosing is highly desirable and has been an important goal for developing next-generation Epo.
Each of the cytokines discussed above, as well as many other cytokines, would benefit from methods and compositions to provide prolonged bioavailability and/or targeting of cytokine to specific cell types, according to the methods and compositions of the instant invention.